Explanation: In a self-biased RF amplifier utilizing grid-leak bias, the operating grid bias is developed by the flow of grid current through the grid-leak resistor. This is a direct application of Ohm's Law. The grid current (I_grid) of 15 mA (or 0.015 Amperes) flows through the grid-leak resistance (R_grid-leak) of 4000 ohms. The resulting voltage drop across this resistor creates the negative grid bias (V_bias). Using Ohm's Law: V_bias = I_grid × R_grid-leak V_bias = 0.015 A × 4000 Ω V_bias = 60 V This 60V makes the grid negative with respect to the cathode, providing the necessary bias for class C or other operating modes. The plate voltage and plate current are not used in calculating grid-leak bias. Therefore, 60 V is the correct operating grid bias.